SI5315 Datasheet, PDF (38/54 Pages) Silicon Laboratories – Provides jitter attenuation and frequency translation between SONET/PDH and Ethemet

Si5315
7. Crystal/Reference Clock Input
The device can use an external crystal or external clock as a reference. If an external clock is used, it must be ac
coupled. With appropriate buffers, the same external reference clock can be applied to CKINn. Although the
reference clock input can be driven single ended (See Figure 18), the best performance is with a crystal or low
jitter, differential clock source. No external loading capacitors are required for normal crystal operation.
3.3 V
3.3 V
130 
CMOS buffer,
8 mA output current
150 
0.1 F
XA
XB
150 
Si5315
10 k
0.6 V
0.1 F
For 2.5 V operation, change 130  to 82 .
Figure 18. CMOS External Reference Circuit
0 dBm into 50 
External Clock Source
0.01 F _XA
Si5315
1.2 V
0.01 F
10 pF
XB
10 k
50 
0.1 µF
0.6 V
Figure 19. Sinewave External Reference Clock Input Example
LVPECL, CML, etc.
100 
0.01 F _XA
Si5315
1.2 V
XB
0.01 F
10 k
10 k
0.6 V
Figure 20. Differential External Reference Clock Input Example
38
Rev. 1.0